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Carotid artery aneurysm secondary to cystic medial necrosis is a rare clinical entity. We report a 59-year-old Chinese male patient who presented with a pulsatile right neck swelling for 2 months. Partial resection of the aneurysm with primary anastomosis of the internal carotid artery was performed. Histopathological examination of the aneurysmal wall demonstrated cystic degeneration of the media with accumulation of glycosaminoglycan material, consistent with the features of cystic medial necrosis. The pathogenesis of carotid artery aneurysm secondary to cystic medial necrosis is discussed.
Keywords: Arterial reconstruction, aneurysmectomy, peripheral aneurysm
J.R.Coll.Surg.Edinb., 46, June 2001, 173-175
Cystic medial necrosis is most commonly reported in patients with Marfan’s syndrome and aortic dissection.1 Cystic medial necrosis of the internal carotid artery leading to the formation of an isolated non-dissecting aneurysm is a rare clinical entity.2,3 We report a case that presented with an asymptomatic neck swelling.
A 59-year-old male patient presented with a 3-cm pulsatile right neck mass which had been present for 2 months (Figure1). It was not associated with pain or other symptoms. Apart from a history of hypertension for 20 years; his previous history was unremarkable. There was no history of neck injury. Marfanoid features were absent on physical examination. The diagnosis of carotid artery aneurysm was confirmed on duplex scan of the carotid arteries. Carotid angiogram revealed an aneurysm at the right internal carotid artery (Figure 2). Magnetic resonance angiogram showed a right internal carotid aneurysm measuring 3 x 4 x 4 cm,3 which contained mural thrombus within the aneurysmal wall.
Figure 1: A pulsatile right neck swelling in a 59-year-old male
Figure 2: Angiogram showing an aneurysm of the right internal carotid artery distal to the bifurcation of common carotid artery
At operation, a saccular aneurysm was found arising from the right internal carotid artery. The distal part of the internal carotid artery was displaced posteriorly, making it inaccessible for distal control. After systemic administration of heparin and the application of an arterial clamp, the aneurysm was opened. Back bleeding from the distal internal carotid artery was controlled by the insertion of a Fr 4 Fogarty catheter with balloon inflation. The aneurysm was partially resected with primary end-end anastomosis of the two ends of the internal carotid artery, using a continuous suture of 6/O Prolene. The patient recovered well and was discharged home on the 4th post-operative day.
Histopathological examination of the aneursymal wall showed areas of atherosclerosis over the intima. Myxoid degeneration was demonstrated in the muscular wall which was consistent with the features of cystic medial necrosis (Figure 3). During follow-up at one year, the patient remained well and asymptomatic. A carotid duplex scan showed no evidence of recurrent aneurysm or carotid stenosis.
Figure 3: The media of the aneurysmal wall showing fragmentation of elastic fibres with deposition of mucoid arterial (haematoxylin and eosin stain, original magnification x245)
Cystic medial necrosis is characterised by the fragmentation of elastic fibres and accumulation of mucoid substance in the media of the arterial wall.4,5 Defective cross-linking of collagen with depletion of elastic tissue in the media is considered to be the fundamental pathology.2 The ineffective repair process of the artery results in a focal accumulation of ground substance, which in turn causes disruption in the continuity of laminae and muscle fibres. The weakened cohesive strength of the media increases the susceptibility of the artery to aneurysm formation.2
In patients without Marfan’s syndrome, cystic medial necrosis occurs more frequently in those with advanced age and chronic hypertension.1,4 It most commonly involves the aorta. Isolated carotid artery aneurysm secondary to cystic medial necrosis has been reported only once on Medline search of the English literature in the past two decades.2 The presence of intimal thickening and fibrosis secondary to atherosclerosis has been postulated to compromise the nutrient vessels supplying the tunica media.6 However, cystic medial necrosis is rarely reported in patients with advanced atherosclerosis. The role of atherosclerosis in the development of cystic medial necrosis remains speculative. The concomitant pathological findings of both atherosclerosis and cystic medial necrosis in our patient could be coincidental.
A pulsatile neck swelling is the commonest presentation of a carotid artery aneurysm.7-9 Other symptoms include pain, transient ischaemic attacks, stroke, hoarseness and dysphagia.10 Differential diagnoses include carotid body tumour, cervical lymphadenopathy, tortuous carotid artery and cervical abscess. The diagnosis of carotid artery aneurysm can be easily confirmed by a non-invasive carotid duplex scan. Arteriography still remains the gold standard in pre-operative surgical planning.9 With advances in radiologic technologies, magnetic resonance angiography has been gaining in popularity. Three-dimensional images can be generated to assess the size of the aneurysm, extent of mural thrombus and anatomical relationship of the aneurysmal neck to the parent artery.
Owing to the potential complications of carotid artery aneurysm, including rupture with fatal haemorrhage and thrombo-embolism with cerebrovascular events, prompt operative intervention is advocated. 5,8,11-16 Complete excision of the aneurysm is not recommended as a high incidence of cranial nerve injuries has been reported.17,18 Restoration of blood flow by primary anastomosis of the two ends of the carotid artery is preferred, whenever feasible.3,8,11 In the event of insufficient length of artery, an interposition graft becomes necessary.
In summary, cystic medial necrosis is a rare cause of isolated carotid artery aneurysm. Carotid artery aneurysm is associated with catastrophic complications and demands early recognition and prompt operative intervention.
Copyright date: 28th November 2000
Correspondence: H. Lau, Department of Surgery, University of Hong Kong Medical Centre, Queen Mary Hospital, 102 Pokfulam Road, Hong Kong
E-mail: lauh@hkucc.hku.hk
©2001 The Royal College of Surgeons of Edinburgh, J.R.Coll.Surg.Edinb.